1. Field of the Invention
This invention relates to a lubricant-containing polymeric synthetic resin composition and a process for preparing it.
2. Description of the Prior Art
Polyamides, polyacetal, polycarbonate and tetrafluoroethylene resins, etc. have previously been used as wear resistant or lubricious plastic materials. These materials are fully serviceable under low loads and at low velocities even in the absence of lubricant supply, but as the load and the velocity become higher, burning and flow occur because of the heat of friction and the materials become useless. Polytetrafluoroethylene has a very low coefficient of friction and undergoes great wear because of a low compression stress. However, when a filler such as glass fibers, asbestos, mica, graphite, lead or lead oxide is incorporated in the polytetrafluoroethylene, its resistance to load is increased, and its wear resistance in the absence of lubricant supply becomes superior. However, such a filled polytetraethylene is very expensive.
In order to improve the wear resistance of cheap polyamides, polyacetal or polycarbonate resins, attempts have been made to fill solid lubricating agents, such as graphite, molybdenum sulfide or a polytetrafluoroethylene powder, in these resins, and some improvement has been attained.
However, in this attempt of incorporating a solid lubricant, the increase in wear resistance under high loads and at high velocities is only slight.
On the other hand, it is well known that in contrast to the absence of lubricant supply, when a lubricant is supplied, the coefficient of friction of the plastic material is reduced to at least 1/10 by the action of the lubricant, and its wear resistance is markedly increased. However, this requires a lubricating mechanism, and the cost inevitably becomes higher because of such an accessory. On the other hand, as regards a metallic material, a sintered porous lubricant-containing bearing obtained by impregnating a lubricant in the bearing itself has been used, and synthetic resins processed somewhat in this way have also been used. However, synthetic resin powders are expensive, and the production of these powders is expensive and gives molded articles of very poor strength with poor moldability.